Numerically controlled engraving machine system

ABSTRACT

A system for automatic simulation by computerized machinery of a hand-engraved pattern in a workpiece. The present system, while concerned primarily in the simulation of engraving patterns by a machine process, nonetheless is applicable to the generation or regeneration of a variety of intricate patterns. In such respect, the process may be useful in copying decorative patterns for printed cards, reproducing of contour maps, and a myriad of other purposes involving the simulation of contours or of a pattern of lines existing in multi-dimensional space. The invention introduces several novel aspects to the art of computerized machinery, and particularly to numerically controlled machinery having multi-axis operation, with one of the major objectives being a reduction of volume of control tape and operation time. The present system usually involves two computers: (1) a digital computer for generating a control tape numerically representative of the pattern to be reproduced; and (2) a digital control computer for controlling a multi-axis machine to regenerate the pattern stored on the control tape.

I United States Patent r191 English et al.

[In 3,857,025 Dec. 24, 1974 NUMERICALLY CONTROLLED ENGRAVING MACHINE SYSTEM [75] Inventors: Myrle II. English, West Chester,

Pa.; Laurence Goodstal, llion, N.Y.; Wayne E. Leek, Mohawk, N.Y.; Robert J. Sanzo, llion, N.Y.; Robert L. Turner, Newark, Del.; Clark B. Workman, Mohawk, N.Y.-; Edward W. Yetter, West Chester, Pa..

[73] Assignee: Remington Arms-Company, Inc.,

Bridgeport, Conn.

[22] Filed: May 7, 1971 [21] Appl. No.: 141,136

[52] US. Cl 235/l5l.l1, 90/13 C, 444/1,

318/568, 33/23 R [51] Int. Cl G05b 19/42, B23c H16 [58] Field of Search 235/151.l1, 152 IE; 33/1 M, 22; 90/13 C [56] References Cited UNITED STATES PATENTS 2,565,914 8/1951 Dies.. 33/22 3,127,506 11/1955 Fayard 235/152 IE 3,559,021 2/1967 Bingham, Jr 235/l51.ll X

3,573,737 4/1971 Rosenberg 235/l5l.1l X

3,609,319 9/1971 Clifford, Jr. et al. 235/l5l.l1

3,628,417 12/1971 Graboyes 3,665,608 5/1972 Stockebrancl 3,746,845 7/1973 Henegar et al.

OTHER PUBLICATIONS fProduction-proved Numerical Control by Ankeney et al., American Machinist, 145-156.

Nov. 4, 1957, pp.

Primary ExaminerEugene G. Botz [57] ABSTRACT A system for automatic simulation by computerized machinery of a hand-engraved pattern in a workpiece.

The present system, while concerned primarily in the simulation of engraving patterns, by a machine process, nonetheless is applicable to the generation or regeneration of a variety of intricate patterns. In such respect, the process may be useful in copying decorative patterns for printed cards, reproducing of contour maps, and a myriad of other purposes involving the simulation of contours or of a pattern of lines existing in multi-dimensional space.

pattern stored on the control tape.

28 Claims, 30 Drawing Figures MOTOR CONTROL CONTROL CONTROL COMPUTER PROGRAM /07 l /05 TAPE //0 INPUT CONTROL TAPE TAPE PREPARATIO N PROGRAM PATENTED 3, 857 025 SHEET 01 0F IA ENORAVINO MACHINE -//0 M M M M M MOTOR CONTROL CONTROL CONTROL OOMPUTER w [07 PROGRAM I f mg TAPE //0 INPUT CONTROL TAPE 4 I TAPE PREPARATION TAPE //04 OUTPUT G A Q I If m3 GRAPHIC MASTER PLOTTING INPUT COMPUTER TABLE Inventdrs:

' Myrfle H. English Laurence GOOdstOI CONTROL COMPUTER Wayne E.'Leek -fi/07 Robert J. Sonzo Robert L. Turner; Mark B. Workman I2 3456789 IOIII2 //3 Edward wiYefler y A //4 I MOTOR TRANSLATOR MOTOR*I AItorneys PATEMEBH 385x25 SHEET UZUF 1'1 Inventors: Myrle H. Engiish Laurence Goodsiol Wu ne E. Leek R0 errJSonzo Roberr L. Turner Clark 8. Workman Edward W. Yetter Attorneys PAIENTEB EM 7 3.57902 $HEET DJUF i4 h h a v ta/6 tnventors= c v Myrte H. English 0 2, X Laurence Goodstol Wayne E. Leek Robert J. Scmzo Robert L. Turner F17. 31;. Clark 8. Workman Edward W. Yetter Attorneys PMENTEB DEC 2 4 I914 SHEET DQUF 1d hnvenirors:

yrle H. Engflish Laurence Gsfol E. Leek ROM JSonzo obefl L. Turner mm B. Workman Edwolr W. Yetter AWOWIHQyS mmmmw m5? 025 SHEET 0 5 HF 14 Myrrm H. English Lauvence Gwdsmi Wayne E. Leek Ruben d. 8mm Haber? L. Turrnev mark B Wmkmon Edwm'd W. Yewev Awomey PATENTED UEEZMQM 3,857,026 SHEET 0706'" 14 i w I I lnventors= Myrle H. English A I Laurence Goodstul A Wayne E. Leek Robert J.Sunzo Robert L. Turner Clark 8. Workman Edward W Yetter AIR HAMMER & CHISEL MANUAL HAMMER 8x CHISEL Attorneys Pmmm mwm 31,857,, 025 I Sim @EUF fifl LOAD RANDOM W m w- NO PARAMETER 1 9 F RESET MACHINE AUX SUBROUTIM FUNCTIONS (AIR OFF, DMSGI cooLANT OFF) REWIND DATA TAPE 7 V SUBROUTINE sToP REWINDING CM 11 SUBROUTINE ZAWR "CONTINUE" PRESSED 5 v E SUBROU'I'INE Q CALL SUBROUTINE W T INIT.

l3 TURN OFF SUBROUTINE -AUX. AND CDWD WAIT IN MOTOR CONTROL FOLLOWING WORD W CW2 LOOP IS INPUT BUFFER FULL Pmmm lim 3, 857', 025

mm as m m coMPuTE FIRST DIFFERENCE IN IDEAL POSITION E2] m FIRST DIFF.

IDEAL POSITION +IDEAL POSITION FIRST DIFF.

PRIOR REMINDER (IN MOTION) MOTION v 12c2\ INTEGER (WHOLE PULSE) PORTION OF MOTION wsws MAGNITUDE OF I'JS l6 CQMPUTE FIRST DIFFERENCE IN WARP V i FIRST DIFF. IN

WARP 111' MOTION W MOTION 12132 REDUCE MAGNITUDE OF WS BY 16 PATENIEBUEC24I9H I mm m m 18A TRANSMIT MOTQR CONTROL WORD A T0 MOTORS E1: E5 Q2 9 18B NO 180 MCW NO 1+1 MOTION 18]) YES PULSES l-wuLsEs I f CLEAR "0N" BIT FROM W NAM 1 MCW w- NAM (D Mcw MOTOR CONTROL wonn i REFERS TO THE ith MOTOR (3D NAM NO. OF ACTIVE MOTOR DRIVES Q9 me STANDBY MOTOR CONTROL WORD PATENTEB EH12 4 I974 ENTER ON INTER- RUPT SUBROUTINE OPER SHEET IMF M READER INTERRUPT READ NEXT CHARACTER OF BLOCK CHARACTER CORRECT CHARACTER (TOUNT YES CORRECT END OF TAPE COUNT YES BEBYTOZS OUTPUT MESSAGES IF ANY DIAGNOSTIC CHARACTER STORE IN INPUT BUFFER START NEXT CHARACTER READING SET KEY FOR FULL INPUT BUFFER START TAPE REWINDING 8c SET END OF TAPE FLAG PATENTEU 0502mm READ:

PATTERN CONTROL DATA J1 0 LOCATION OF PATTERN REFERENCE POINT (RELATIVE TO X AND Y AXES OF PATTERN DATA) 0 PATTERN X AND Y SCALE FACTORS (NEG. VALUES PROVIDE MIRROR IMAGING) o MAXIMUM DEPTH AND TILT OF CUTS 3 MISCELLANEOUS CONTROL CODES & DATA FOR SUBROUTINE CONv STARTING LOCATION TO WORK PIECE WHEN NEW WORK PIECE IS LOADED CALL SUBROUTINE CONV (CONVERT) TO ADJUST (THE STARTING POINT IN THIS CASE) FOR PATTERN I 32 CENTERING (RE: PATTERN REFERENCE POINT), MIRROR IMAGING, AND IF NECESSARY, CONVERT FROM FLAT PATTERN COORDINATES TO MACHINE COORDINATE-S (I.E., POINTS ON, OR SLIGHTLY DELOw THE ACTUAL METALSUREACE) ALL SUBROUTINE CRIT "CRITICAL" POINT) TO READ A sEQUENCE OF- POINTS REPRESENTING A CUT SEGMENT (OR A COMPLETE CUT) CRIT IN TURN CALLS SUBROUTINE CONV TO ADJUST EACH POINT END DATA

SUPPLY ENDING" SEQUENCE TO OUTPUT.

PATENMU HEM EM ESELOEE SHEET 13305 M CALL SUBROUTINE PANDSL (POINT AND SLOPE) TO DETERMINE SLOPE, WITH RESPECT TO CUT LENGTH, FOR EACH AXIS AT EACH END OF THE CUT SEGMENT COMPUTE NORMAL POLYNOMIAL COEFFICIENTS FOR AXES X, Y, Z AND (1 (BASIS NO. STEPS 100) TEST FOR EXCESSIVE Z(DEPTH) OR @(TILT) AT ANY POINT THRUOUT CUBIC CUT SEGMENT. REDUCE WAS Z OR 0L EXCESSIVE SLOPES AT ENDS OF SEGMENT IF NECESSARY.

CALL SUBROUTINE ERRCHK TO DETERMINE IF X AND Y POLYNOMIALS DEFINE CURVES WHICH ADEQUATELY MATCH THE DATA POINTS. IF ERRORS ARE EXCESSIVE, SET SEGMENT SUBDIVISION FLAG AND EFFECT SUBDIVISION.

DIVISION FLAG SET CALL SUBROUTINE COONS (PROF. s. A. COONS, MIT) PATENIEB DEEZMQM FIRST EN 12 T n s; V SEGP-fluNl W GENERATE OUTPUT BLOCK 'rofl u 01" CUT TO CAUSE "TOOL-UP" GENERATE OUTPUT BLOCK TO MOVE TO NEW CUT GENERATE OUTPUT BLOCK TO CAUSE "TOOL-DOWN" I-OC CONVERT NORMAL POLYNOMIAL COEFFICIENTS TO fAOD' DIFFERENCE COEFFICIENTS (BASIS NO. STEPS 100) ADJUST NO. STEPS, IF NECESSARY, TO OBTAIN DESIRED RESOLUTION IN ACTUAL MACHINE OPERATION AND/OR IOE COMPLY WITH RESTRICTIONS IN, AND PRECISION IMPOSED BY MACHINE CONTROLLER COMPUTER PROGRAM. IF NO. STEPS CHANGED, RECOMPUTE DIFFERENCE COEFFICIENTS GENERATE OUTPUT BLOCK CONTAINING; SEQUENCE f LOF NO., NO. OF STEPS, AND CUBIC DIFFERENCE COEFFICIENTS PLOT THE CUT SEGMENT AS RECONSTRUCTED FROM THE f lOG CUBIC DIFFERENCE COEFFICIENTS MON LAST

SEGMENT CUT YES 'sAvE RECONSTRUCTED LAST POINT FOR USE IN COMPUTING MOTION TO REACH NEXT CUT NUMERICALLY CUNTROLILIEI) ENGIRAVING MACHINE SYSTEM The present invention pertains to simulating by computerized machinery a hand-engraved pattern in. a

workpiece, which is visually and aesthetically comparable to the original design.

In the past, the production of engraved designs on hard and tough metals such as steel could only be accomplished by hand, requiring highly skilled artisans. Unfortunately, modern times have seen the erosion of many specialized techniques such as engraving, which requires highly skilled personnel. I

The scarcity and high cost of experienced people has made engraving on steel prohibitive in all except a few applications, such as, printing plates for bank notes and high-priced firearms.

As a result of this trend,-substitute methods were sought to simulate the engravers art. Embossing by rolls or stamps, and metal removal techniques employing conicalend-mills or routers were tried. These methods were only nominally successful, because the visual effects of the engraving cut could not be duplicated by any other tool except that used by the engraver. In other words, the pleasing pattern of hand-engraving depends upon the detail geometry and the surface finish of the cut.

Finally, thought was given towards using machinerywith the same tools and metal removal techniques as those used in hand-engraving. It wasrealized that the complexities of each cut in the pattern could be handled by computer-controlled methods. In addition,

computerized methods were required not only to overcome the complexity of the operation, but equally to speed up the process and thereby reduce costs.

The adoption of computer techniques to regenerate an engraving pattern, however, was no small task. To begin with, the various motions of the engravers tool in making each cut hadto be carefully scrutinized. Then, in order that a machine could guide a machine tool to duplicate the hand-held tool motions, these motions had to be defined and expressed in-mathematical terms. Equations were derived to define the coordinates of the various toolmotions. The coefficients for each equation were derived for each cut or cut segment by means of a digital computer.

To regenerate an entire pattern, a tape is generated by the computer with all the numerical indicia necessary to reproduce every cut sequentially. This tape is fed to a digital control computer whose output controls a machine guiding the relative motion of the engraving tool with respect to the workpiece.

One of the novelties of this invention is its mathematical approach to the engraving problem. A new mathematical concept developed by Professor Steven A. Coons, of the Massachusetts Institute of Technology, (Electronic Systems Laboratory Memorandum MAC- M-253 was useful in the solution to engraving simulation. Professor Coons demonstrated that contours can be expressed in terms of third degree or higher ordered polynomials, each having a common parameter.

The motion of a hand-held engraving tool making a cut in a workpiece was analyzed and then broken down into component motions expressed as mathematical variables. A polynomial equation was written for each variable, and the coefficients for each polynomial were derived. The coefficients were expressed as difference coefficients so that their generation or regeneration requires only an addition operation rapidly implemented on a small computer.

The variables describing the tool motion relate to the tool angle in rotation and tilt, the depth of cut in the workpiece taken by the tool, and the coordinates which define the path of the tool in making the cut.

Having established a computer system for converting tool motions into numerical indicia and then regenerating these motions by means of a control computer, it is possible to reproduce any design or pattern whose lines exist in multi-dimensional space. The visual characteristics of the machining or marking process will depend upon the nature of the tool used. In other words, a printed design or emblem may be reproduced by. means of a pen or marking-type element. Likewise, the repro duction of intricate surface contours may require the use of a routing-type element. As long as any particular tool motion can be analyzed, the present computer system can be used to reproduce the design.

' It is an object of this invention to provide a computerized system forgenerating a line course existing in multi-dimensio nal space.

It is another object of thisinvention to provide a It is still another object of this invention to reduce the amount of stored information required to generate or regenerate a. patternof lines existing in multidimensional a space.

These and other objects of this invention will be better understood and will become more apparent with reference to the detailed description and drawings in which:

FIG. I is a schematic diagram of the complete com-. puterized engraving system;

FIG. la is a schematic diagramof the motor system of FIG. ll;

FIG. 2 is a plan view of a typical engraving cut;

FIG. 2a is a'sectional view of the'engraving cut of FIG. 2 sliced at various sections along its length;

FIG. 2b is a plan view of the cut of FIG. 2 made on a block of metal;

FIG. 20 is an isometric view of the cut block as shown in FIG. 2b;

FIG. 2d is an enlarged macroscopic view of a section of the cut shown in FIG. 2c;

FIG. 3 is a view of an air-hammer and an engraving chisel making a cut in a metallic block;

FIG. 3a is an isometric view of the engraving chisel of FIG. 3, making a cut;

FIG. 3b is a side view of the-engraving chisel making the cut of FIG. 3a;

FIGS. 3c through 3e are views showing the geometry of the cut and the engraving chisel of FIG. 3a, wherein:

drive in the metal FIG. 30 shows a plan view of a sectionof the cut;

FIG. 3d is a cross-sectional view of the chisel face and the workpiece; and

FIG. 3e shows an isometric view of the chisel making a .cut in the workpiece;

Flg. d is an isometric view of the embodiment of the engraving machine;

FIG. is a schematic view of a particular modification of the machine of FIG. 4; I

FIG. 6 is an isometric view of another embodiment of the engraving machine illustrated in FIG. 4;

FIG. 7 is a schematic view of two particular features of the machine of FIG. 6;

FIG. 8 is a full scale view of an engraving pattern plotted by the digital computer plotting table;

FIG. 9 is a view of a portion of the plot of FIG. 8 shown at 10 times scale;

FIG. 10 is a developed longitudinal sectional view of a typical border cut;

FIG. 10a is a developed longitudinal sectional view of a typical scroll cut; I

FIG. 11 is an isometric view of the carriage portion of the machine shown in FIG. 4; and

FIG. 12 is a view of surface tracings, respectively, of a machine-made and a hand-made engraving cut.

FIG. 13 is a flow chart of the controller control program for regeneration of successive segments of cuts and miscellaneous tool motions;

FIG. 14 is a flow chart in a controller control background program for computation of motion for each axis;

FIG. 15 is a flow chart of a control program subrou tine to operate the drive motors;

FIG. 16 is a flow chart of a control program for interrupt handling; and

FIGS. 17-19 are flow charts of the master computer program for determining and storing coefficients of continuous polynomial functions defining line courses existing in multidimensional space.

Broadly speaking, the invention contemplates the method of generating or regenerating a line course existing in multi-dimensional space.

In generating a line course existing in multidimensional space, a plurality of continuous polynomial funcmethod of regeneration is the expression of an engraved pattern in terms of numerical indicia. These indicia are fed to the digital control computer which is programmed to control the axis motors of a machine having a power driven reciprocating engraving tool. The axis motors control the powered engraving tool simulative of the motions of a hand-held tool about a workpiece.

The motion of a hand-held engraving tool making a cut in a workpiece may be translated into numerical indicia by defining a tools overall motion as a plurality of component motions.

For an engraving cut in a flat workpiece, the component motions are expressed as independent variables:

tions having a common parameter are selected. The

functions so selected are descriptive of the respective coordinates definingthe line course. A digital computer is utilized to determine the coefficients for each of the polynomial functions.

Next, the coefficients are stored.

Then, the coordinates defining said line course are respectively generated as successive sequential increments from said stored coefficients.

A preselected line course is similarly regenerated by selecting the polynomials to fit the particular line course.

More specifically, the regeneration of said line course is for one of a pattern of lines existing in multidimensional space, and is regenerated by a double computer operation as follows:

A digital computer input is prepared which is an expression of the preselected line of said pattern. Next, a digital computer .is utilized to determine the coefficients of the previously mentioned polynomials. A control type including said coefficients is prepared by the computer. v

A digital control-computer is fed the control tape. The control computer is programmed to be responsive to the coefficients so as to direct the motions of a plurality of axis motors. A machine having a regenerating element controlled by said axis motors is caused to regenerate the line course.

As applies explicitly to the simulation of a preselected hand-engraved pattern in. a workpiece, the

X, Y, Z and oz, and a dependent variable 0, where:

Xis the lateral motion of the tool substantially parallel to the face plane of the workpiece;

Y is the motion of the tool perpendicular to X and substantially parallel to the face plane of the workpiece:

Z is the depth motion of the tool substantially perpendicular to the face plane of the workpiece; a is the tilting motion of the tool about an axis passing through the cutting tip of the tool and substantially parallel to the face plane of the workpiece; and

0 is the rotational motion of the tool about an axis passing through the cutting tip of the tool and substantially perpendicular to the face plane of the workpiece, and further wherein 6 is theheading of the tool defined as the angle of the tangent to the tool path at the cutting tip of the tool.

For an engraving cut in a cylindrically-shaped surface of a workpiece, whose cylindrical surface is created by a generating element, the component motions are expressed as independent variables: X, Y,, Z and a, and a dependent variable 0, where:

X is the lateral motion of the tool substantially parallel to the generating element of said surface;

Y, is the motion of the tool substantially parallel to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool, and substantially perpendicular to the generating element of said surface;

Z is the depth of the tool substantially perpendicular to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool;

a is the tilting motion of the tool about an axis passing through the cutting tip of the tool and substantially parallel to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool; and v 0 is the rotational motion of the tool about an axis passing through the cutting tip of the tool and substantially perpendicular tothe plane tangent to the curved surface of the workpiece at the cutting tip of the tool, and further wherein 6 is the heading of the tool defined as the angle of the tangent to the tool path at the cutting tip of the tool.

The variables are introduced to the digital computer as coded data.

The X and Y data points along the cut are utilized to develop the string length u according to the following formula:

II uh: EV F 'l' i where:

t i i-l Next, the computer is programmed to generate the dependent variable 6 which represents the tool heading in accordance with a formula of the type:

As was aforementioned, the variables are then expressed as a plurality of continuous polynomials having a common parameter.

In our case, we chose the string length u as the common parameter for the variables:

Thus, the polynomials are expressed as: X=a +bu+cu +du Y=e +fu+gu +hu Z=i+ju+ku +lu =m+nu+'pu +qu a= "r+su+tu +vu The computer derives the coefficients of the polynomials and stores themfor input into the control computer.

Professor Coons has specified that third degree or higher polynomials are adequate to define any contour.

Actually, the degree selected is a matter of choice, and depends upon the economics of operation. In other words, the amount of tape generated will be dependent upon the degree selected for the polynomials defining each cut. While a higher degree polynomial requires more coefficients, this set of coefficients may be adequate'to produce a longer cut, and thus, may actually reduce the overall number of coefficients required to produce a complete pattern.

In our case, it" is convenient to select third degree polynomials as they are usually adequate to regenerate any line course existing in multi-dimensional space, except for straight line motions.

, The computer is programmed to generate a polynomial of predetermined degree for each variable. If the. variable X along a segment of the curve is a straight line, a first degree of polynomial would be adequate. Then too, for straight motions of the tool not involving cutting, i.e., where the tool is moving from one cut to another cut, or up or down at the beginning or end of each cut, a first degree polynomial is also sufficient.

In general a polynomial cannot duplicate exactly an arbitrary curve as defined by a series of points. In our case exact duplication is not necessary and the generated line is allowed to deviate by a predetermined tolerance. Thus, in comparing the generated polynomials with the data points, the computer will subdivide the cut into segments dependent upon the allowable departure tolerance. Thus, several segments may be required a to regenerate any particular cut on the control computer.

It should be noted, in engraving, the determination of tolerance limits and the resultant degree of subdivision of cuts depends on aesthetic considerations such as the desirability of producing long sweeping curves rather than blindly reproducing the data points.

The coefficients obtained in determining the polynomials are stored on the control tape with data referring to the number of increments needed for regeneration of the cut, and the degree of polynomial for all axes. These data are then fed to the control computer which is programmed in accordance with the following flow chart:

Read data for one segment of a cut Deterr uine for each motor,

motion for one increment number pulses and direction of Drlve motors Determine which, if any, motors require additional pulses.

Iflnot If any require additional pulses Lm i Determine if any increments remain If not i I l l l The above continues until all data are exhausted.

If any remain The output of the control computer controls a plurality of axis motors. Each axis motor in turn controls the relative motion of the engraving tool about the workpiece for that particular axis variable. The engraving tool is powered by an air-hammer as a substitute for the pattern. The master computer 1100 has a program 1103 to prepare a control tape lltlS by means of the tape output 1104-. This control tape is then fed to the tape input device 106 of a small digital control computer 1107. The control tape is shown in this embodiment as a perforated tape, but it is possible to store the data. in other media such as magnetic tape, a magnetic drum, punched cards, etc. I

The control computer 1107 has a control program 1108 that directs said computer in' the arithmetic and logic functions necessary to control all the motions of the engraving machine 1110 in accordance with the abbreviated information on the control tapefThe control computer W7 has a motor control output 109 which drives a plurality of controlled axis motors designated M (five illustrated) contained within the engraving machine lllltl.

FIG. lla depicts a suitablemotor drive system for the system illustrated in FIG. ll. The digital control computer W7 is arranged so that a computer word (let us assume for convenience 12 bits) may be outputted directly from the accumulator (not shown) of the computer M7 to an external register 113. The output word format is such that-bits l and 2 are designated to control a First Axis Motor i112, bits 3 and t are designed to control a Second Axis motor (not shown), and so on for the five axis motors of engraving machine 110.

Stepper motors have been used for all control axes, because of their simple electrical drive requirements, although it is possible to use other types of motors by suitably modifying the system. Specifically, a l in bit position l, in the form of an electrical impulse, when applied to the motor translator ill, will drive the First Axis motor llllZ one step in the positive direction. A l positioned in bit position 2 will similarly drive the motor 1lll2 one step in the opposite direction.

Naturally, if an appears in the register 113 at both bit positions, the motor will remain stationary. The simultaneous occurrence of a l in both bit positions is a prohibited condition in this system. The configuration of the first 10 bits of the computer word completely determines the operation of all five motors of the engraving machine 110. The repetition rate of the word output will determine the speed of the motors.

The engraving machine 110 has five axis motors, since it has been determined that the motion of a handheld engraving chisel making a cut in a workpiece can be broken down into five component motions. Thus, a machine controlled engraving chisel can simulatively respond in like fashion to a hand-held tool, by controlling its motion in the five so determined component axes.

In the general area of line course regeneration, different tool motions may be similarly analyzed and broken down into component motions. Thus, the present system may conceivably be used to guide different machine elements in a myraid of operations such as: printing, machining, marking, milling, scratching, shaping, routing, etc. These other machining techniques can use the same general mathematical approach and computer system. They may require, however, the same, or a greater or lesser number of axis motors to simulate the particular component motions of the specific machine element.

In the present engraving system, it will be noted that the last 2 bits (11 and 12) of the register 113 are not used for motor control, .but they may be decoded in 114 to control other machine functions, such as controlling the required air supply to power the airha'mmerthat drives the engraving chisel, or the amount of coolant flowing to the cutting tip of the chisel.

The overall system requirements and performance may be better understood by examining in detail the characteristics of hand-engraving. It' will then become apparent what is required of a machine tool in simulating the hand-engraved pattern.

Reference is made to FIGS/2 and 2b, which show a typical engraving cut sliced at various sections along its length.

In hand-engraving, the cut is made in the metal with a'V-pointed chisel 30 as illustrated in FIGS. 3a and 3b. The chisel is' forced to remove the metal by successive hammer blows resulting in the surface finish and cut geometry characteristic of hand engraving, and often producing a faceted sidewall in curved cuts as shown in FIGS. 2d and 3a.

FIG. 2dd is an enlarged macroscopic view of a section of the engraving cut 20 of FIG. 20. Facets 21 have been cut in the metal by the engraving chisel. These facets in addition to the surface finish and cutting geometry give an aesthetically pleasing quality to the cut that cannot be duplicated by embossing, routing, or other simulative techniques.

The V-shape d engraving chisel 30 produces a cut with a V-shape profile 22 as shown in FIG. 20.

Because the engraver continually adjusts the angle of his chisel with respect to the workpiece as he proceeds to hammer out his cut, this V-shape profile changes along the length of the cut. FIG. 2a illustrates the changing V-shaped profile of the cut shown in FIG. 2. The varying cross-sections are shown for slices made in the cut at sections a through d, respectively. The changing nature of this cross-section profile is known as siding, and further distinguishes the appearance of the engraving cut from those made by other machining methods. I

It should also be mentioned that the width of the cut in influenced by the tilt of the tool with respect to the workpiece.

It is obvious, therefore, that the simulation of a handengraved pattern is dependent upon:

a the shape of the chisel;

b the successive hammer blows producing the surface finish of the cut; and c the geometry of the tool relative to the workpiece.

It was determined that a chisel 30 (FIG. 3) with a cutting face of approximately included angle, driven by a reciprocating mechanism, such as an air or electric hammer 31, will reproduce or otherwise simulate the surface finish of hand chisels.

It was also discovered that the powered engraving too] could be run at a greater cutting speed than a hand-held tool and yet preserve the aesthetics and quality of the engraving cut. The increase in cutting speed was essential for obtaining economical production rates.

FIG. 12 shows a surface profile tracing of a portion of an engraving cut made by the powered engraving tool, and the hand-held tool, respectively. As will be observed, the two .cuts have almost identical surface finish characteristics, thus demonstrating that the cut made by a powered tool can simulate the surface finish of a hand-held engraving cut, as was aforementioned. Since the surface finish of thecut determines to a large extent the light reflectance characteristics, the visual appearance of a cut made by a power tool can be made essentially identical to that made by a hand-engraving tool.

In confirmation of this, it should also be noted that no visual distinctions were observed between the two cuts, when examined by experts of the engraving art.

FIG. 3e is illustrative of the geometry of the tool making an engraving cut me workpiece. It is to be em phasized that the tool motions are analyzed relative to the workpiece, and not to any external frame of reference.

The top view of the cut is shown in the X, Y plane (FIG. 3c) with the cutter motion from left to right relative to the workpiece. The path of the cutter point 23 (FIG. 3:1) is shown as line aa', and the intersection 24 of the cutter face 25 with the surface 26 of the workpiece is shown as lines bb' and c-c'.

At the point X Y the position of the cutter relative to the workpiece is as follows:

a. the cutter point is located at a point X,, Y 2,, in

the coordinate frame in which the X and Y axes are located on the surface of the workpiece and the Z axis extends downward from the workpiece surface;

b. the cutter heading, i.e., the cutting direction, is along the tangent to the cut at point X Y,, at an angle 0 to the reference; and

c. the cutter face is tilted'at an angle a from the vertical, about a horizontal axis through the cutter point. Although there is no limitation to the tool tilt motion about the horizontal axis, it has been found convenient for our machine embodiments to restrict the tilt motion to an axis parallel to the tool heading. However, for other engraving applications it may be desirable to position the tilt axis at some angle to the tool heading, or to provide additional tilt motion.

Since the value of each of the coordinates X, Y, Z, 0, a, will, in general, change during the cutting process, each one must be treated as a variable. It is convenient, as will be demonstrated later, to express each variable mathematically as a function of a common parameter, the length u along the cutter point path, thus:

The required geometry of the cutter relative to the workpiece will determine the basic geometry of the machine tool motions. Thus, the following relative motions are required:

a. the cutter must be positioned to any point in the X,- Y plane, over a range encompassing the entire area of the engraved pattern;

b. the cutter must be positioned in the Z direction to any point from the surface of the workpiece downward to the maximum depth of cut; Additional latitude of movement will be required in the X, Y, and Z motions as regards a working machine tool to allow clearance for workpiece replacement.

c. the heading of the cutter (i.e., the forward direction of cutting) must be rotatable in a full 360,

' relative to the workpiece, to allow a cut in any direction in the surface of the workpiece. In a practical machine, continuous rotation capability is desirable.

d. the cutter face must be tilted through angle a, in a vertical plane, the amount necessary to provide the proper degree of siding in the cut. In both the angular motions described, it is desirable to arrange these motions so that each rotation takes place about the cutter point as a center. Thus, the rotation 74 takes place about a vertical axis, and the rotation or takes place about a horizontal axis, with the two axes intersecting at the cutter point. It is obvious in view of the aforementioned geometries of the cutting tool and surface, this restriction eliminates any interaction of variables a and 0 with X, Y or 'Z.

An additional requirement applicable to all five axes of motion is the necessity for providing smooth, continuous motion in all axes simultaneously, in accordance with the appropriate f (u); n

It should be obvious to those skilled in the art that the requirements of relative motion described above may be implemented by several machine configurations. Two preferred configurations will be described herein.

FIG. 6 shows a machine suitable for engraving rela- I tively small workpieces. The workpiece 40 is the receiver of a firearm, and is restrained in vise 41 mounted on table 42. The machine is constructed to provide rectilinear motion along the X and Y axes, and rotational motion to thetable 42 about vertical axis 83. The rectilinear motions X and Y are provided by a double crossslide arrangement 42 and 43 whichis shown schematically in FIG.- 7. The entire cross-slide arrangement is mounted on bearings so that it may rotate about a vertical axis to provide for the 0 variable. Driving motor 44 operating through lead screw 45 moves the workpiece lltll withrespect to the X axis. Similarly, driving motor 66 operates through lead screw 47 to move the workpiece along the Y axis. Drive motor 48 operates the worm gear arrangement 19 to provide rotation (6) for the workpiece about a vertical axis intersecting the tool point. The air-hammer drives the engraving chisel 52, and is mounted on an overhead arm 51. The arm 5l is mounted on a rotatable head 53 to provide tilting motion (or) of the tool about horizontal axis 84- with respect to the workpiece. This mounting arrangement produces a horizontal axis of rotation for the tool which intersects both the cutter point and the vertical axis of rotation of the X and Y cross-slide. The entire arm and rotatable head assembly are mounted on a vertical slide 54, thus providing for motion along the Z axis. The driving means for the (1 axis is motor 57 coupled through, preferably, a worm gear arrangement 5&The vertical slide 54 is driven by motor 55 and vertical lead screw 56.

As was aforementioned, several motor types may be used to power-all five of the axes of the machine. The use of stepper motors, however, has been found to be particularly convenient.

Another machine embodiment is shown in FIG. 4. This machine incorporates the same geometrical relationships of tool and workpiece, but is designed to handle larger workpieces than the machineof FIG. 6. A receiver 40 is mounted as before upon a double crossslide arrangement to furnish motion along the'X and Y axes, respectively. The base of the cross-slide unit, however, is rigidly fixed to the machine base 62 at points M. The chisel 52, and its air-hammer 50], is mounted on a carriage 65 constrained to move over a portion of a circular path by means of arcuate guide rails '63 and 641, respectively. (Also see FIG. 11). The

rotation of the tool has the center of the are located at the cutting tip of the chisel 52. This provides for the tilt motion, or (1 axis. The carriage assembly 65 is supported upon a rotatable spindle 66,'thus providing the 6 axis motion. The combination of the spindle 66 and the tiltable carriage 65 is supported on movable frame 67, which is moved along the Z axis by lead screw 68.

One of the majordesign differences between the two the workpiece; It is deemed by the inventors that-any modifications of this nature lie within the scope and purview of this aspect of the invention.

As in the previously described embodiment of FIGS. 6, the X and Y motion is provided by steppermotors 70 and HI, respectively, acting upon lead screws 72 and 73, respectively. The lead screw 68 for the Z axis is also activated by a stepper motor (not shown).

The 0 motion may be provided by gearing, or by a chain and sprocket drive 69 driven by motor 76, as shown. The tilting motion (a) is produced by a spiral bevel pinion 741 acting upon the gear sector 75 as depicted in FIG. II. The motor '77 driving the spiral bevel pinion 76 is mounted on the upper portion of the rotat- 

1. The method of translating into numerical indicia the course of a hand-held engraving tool having a tip making an engraving cut in the face plane of a substantially flat workpiece so that said cut may be automatically simulated by a computer-controlled, powered engraving tool, comprising the steps of: a. defining the course of the hand-held tool as a plurality of component motions given as independent variables X, Y, Z, Alpha , and a dependent variable where: X is the lateral motion of the tool substantially parallel to the face plane of the workpiece; Y is the motion of the tool perpendicular to X and substantially parallel to the face plane of the workpeice; Z is the depth motion of the tool substantIally perpendicular to the face plane of the workpiece; Alpha is the tilting motion of the tool about an axis passing through the cutting tip of the tool and substantially parallel to the face plane of the workpiece; and theta is the rotational motion of the tool about an axis passing through the cutting tip of the tool and substantially perpendicular to the face plane of the workpiece, and further wherein theta is the heading of the tool defined as the angle of the tangent to the tool path at the cutting tip of the tool; b. defining each variable as a function of a common parameter: the string length ''''u'''' along the cutter point path, thus: X fx (u) Y fy (u) Z fz (u) theta f (u) Alpha f (u); c. expressing each variable as a polynomial in u; such as: X a + bu + cu2 + du3 + . . . Y e + fu + gu2 + hu3 + . . . Z i + ju + ju2 + lu3 + . . . theta m + nu + pu2 + qu3 + . . . Alpha r + su + tu2 + vu3 + . . . d. programming a digital computer to derive the coefficients of the polynomial equations of (c); e. deriving by means of said digital computer said coefficients and f. controlling the course of the powered engraving tool by means of said coefficients to regenerate the course of said hand-held engraving tool making an engraving cut.
 2. The method of claim 1, wherein said computer is programmed to process an input containing coded digital information descriptive of a cut in an engraving pattern and provide an output of stored coefficients of a plurality of continuous polynomials descriptive of said cut, comprising the steps of: a. providing the input of said computer with data containing the following: X points along the engraving cut, Y points along the engraving cut, Z points along the engraving cut, Alpha points along the engraving cut; b. computing the string length (un) along the cut as determined by the X and Y points in accordance with the following formula:
 3. The method of claim 1, further comprising the step (f) of storing said coefficients.
 4. The method of claim 1, further comprising the step (f) of storing said coefficients in a medium consisting of one of the following: a perforated tape, a magnetic tape, a magnetic drum, and punched cards.
 5. The method of claim 1, further comprising the steps of: f. storing said coefficients; and then g. regenerating from said stored coefficients the cutting motions of said powered engraving tool relative to the workpiece.
 6. The method of claim 1, wherein said coefficients are difference coefficients.
 7. The method of translating into numerical indicia the course of a hand-held engraving tool having a tip making an engraving cut in the substantially cylindrically shaped surface of a workpiece created by a generating element so that said cut may be automatically simulated by a computer-controlled, powered engraving tool, comprising the steps of: a. defining the course of the hand-held tool as a plurality of component motions given as independent variables X, Yr, Z, and Alpha , and a dependent variable theta , where: X is the lateral motion of the tool substantially parallel to the generating element of said surface; Yr is the motion of the tool substantially parallel to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool, and substantially perpendicular to the generating element of said surface; Z is the depth motion of the tool substantially perpendicular to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool; Alpha is the tilting motion of the tool about an axis passing through the cutting tip of the tool and substantially parallel to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool; and theta is the rotational motion of the tool about an axis passing through the cutting tip of the tool and substantially perpendicular to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool and further wherein theta is the heading of the tool defined as the angle of the tangent to the tool path at the cutting tip of the tool; b. defining each variable as a function of a common parameter: the string length ''''u'''' along the cutter point path, thus: X fx (u) Yr fyr (u) Z fz (u) theta f (u) Alpha f (u); c. expressing each variable as a polynomial in u, such as: X a + bu + cu2 + du3 + . . . Yr e + fu + gu2 + hu3 + . . . Z i + ju + ku2 + lu3 + . . . theta m + nu + pu2 + qu3 + . . . Alpha r + su + tu2 + vu3 + . . . d. programming a digital computer to derive the coefficients of the polynomial equations of (c); e. deriving by means of said digital computer said coefficients; and f. controlling the course of the powered engraving tool by means of said coefficients to regenerate the course of said hand-held engraving tool making an engraving cut.
 8. The method of claim 7, wherein said computer is programmed to process an input containing coded digital information descriptive of a cut in an engraving pattern and provide an output of stored coefficients of a plurality of continuous polynomials descriptive of said cut, comprising the steps of: a. providing the input of said computer with data containing the following: X points along the engraving cut, Yr points along the engraving cut, Z points along the engraving cut, Alpha points along the engraving cut; b. computing the string length (un) along the cut as determined by the X and Yr points in accordance with the following formula:
 9. The method of claim 7, further comprising the step (f) of storing said coefficients.
 10. The method of claim 7, further comprising the step (f) of storing said coefficients in a medium consisting of one of the following: a perforated tape, a magnetic tape, a magnetic drum, and punched cards.
 11. The method of claim 7, further comprising the steps of: f. storing said coefficients; and then g. regenerating said stored coefficients for directing the cutting motion of said powered engraving tool relative to the workpiece.
 12. The method of claim 7, wherein said coefficients are difference coefficients.
 13. A method of simulating a preselected hand-engraved pattern in a workpiece by automatic means, comprising the steps of: a. expressing the preselected hand-engraved pattern in terms of numerical indicia as input into a digital control computer; b. introducing the numerical indicia to the input of said digital control computer; c. directing said digital control computer by means of a control program based upon said numerical indicia to control an engraving machine having a power driven reciprocating engraving tool and a plurality of axis motors positioning the movements of the engraving tool operative on a workpiece simulative of the motions of a handheld tool operative on a workpiece wherein a digital computer is programmed to process an input containing coded digital information descriptive of a cut of an engraving pattern made by an engraving tool having a cutting tip making said cut in the face plane of a substantially flat workpiece, and provide an output of coefficients of a plurality of continuous polynomials descriptive of said cut for input into said control computer, comprising the steps of: a. providing the input of said computer with data containing the following: X points along the engraving cut, Y points along the engraving cut, Z points along the engraving cut, Alpha points along the engraving cut, wherein: X is the lateral motion of the tool substantially parallel to the face plane of the workpiece; Y is the motion of the tool perpendicular to X and substantially parallel to the face plane of the workpiece; Z is the depth motion of the tool substantially perpendicular to the face plane of the workpiece; and Alpha is the tilting motion of the tool about an axis passing through the cutting tip of the tool and substantially parallel to the face plane of the workpiece: b. computing the string length (un) along the cut as determined by the X and Y points in accordance with the following formula:
 14. The method of claim 13, wherein said digital control computer is programmed to iteratively process an input containing stored coefficients of a plurality of continuous polynomials descriptive of the engraving cuts in said hand-engraved pattern, to thereby provide an output of control signals directing the motion of a said engraving tool so as to simulate, by successive sequential increments, said engraving cuts, comprising the steps of: a. introducing said coefficients into said digital control computer: and then: b. generating said control signals from said coefficients by iterative computation.
 15. The method of claim 14, wherein said coefficients are difference coefficients, and the iterative computation comprises a series of summations of said difference coefficients to regenerate successive sequential increments of the engraving cuts.
 16. The method of claim 13, further comprising the step of storing the numerical indicia prior to its input into said digital control computer.
 17. The method of claim 16, wherein said numerical indicia are stored in a medium consisting of one of the following: a perforated tape, a magnetic tape, a magnetic drum, and punched cards.
 18. The method of claim 13, wherein said numerical indicia comprise coefficients of a plurality of continuous polynomial functions having a common parameter, said functions being descriptive of the coordinates defining the cutting paths of the engraving tool in simulating said preselected pattern.
 19. The method of claim 18, whrein said coefficients are difference coefficients.
 20. The method of claim 19, wherein said difference coefficients are summed under the direction of said control program to control the motion of said axis motors.
 21. A method of simulating a preselected hand-engraved pattern in a workpiece by automatic means, comprising the steps of: a. expressing the preselected hand-engraved pattern in terms of numerical indicia as input into a digital control computer; b. introducing the numerical indicia to the input of said digital control computer; and c. directing said digital control computer by means of a control program based upon said numerical indicia to control an engraving machine having a power driven reciprocating engraving tool and a plurality of axis motors positioning the movements of the engraving tool operative on a workpiece simulative of the motions of a handheld tool operative on a workpiece wherein a digital computer is programmed to process an input containing coded digital information descriptive of a cut of an engraving pattern made by an engraving tool having a cutting tip making said cut in a substantially cylindrically shaped surface of a workpiece created by a generating element and provide an output of coefficients of a plurality of continuous polynomials descriptive of said cut for input into said control computer, comprising the steps of: a. providing the input of said computer with data containing the following: X points along the engraving cut, Yr points along the engraving cut, Z points along the engraving cut, Alpha points along the engraving cut, wherein: X is the lateral motion of the tool substantially parallel to the generating element of said surface; Yr is the motion of the tool substantially parallel to the plane tangent to the curved surface of the workpiece at the cutting tip of the too, and substaNtially perpendicular to the generating element of said surface; Z is the depth motion of the tool substantially perpendicular to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool; Alpha is the tilting motion of the tool about an axis passing through the cutting tip of the tool and substantially parallel to the plane tangent to the curved surface of the workpiece at the cutting tip of the tool; b. computing the string length (un) along the cut as determined by the X and Yr points in accordance with the following formula:
 22. The method of claim 21, wherein said digital control computer is programmed to iteratively process an input containing stored coefficients of a plurality of continuous polynomials descriptive of the engraving cuts in said hand-engraved pattern, to thereby provide an output of control signals directing the motion of a said engraving tool so as to simulate, by successive sequential increments, said engraving cuts, comprising the steps of: a. introducing said coefficients into said digital control computer; and then: b. generating said control signals from said coefficients by iterative computation.
 23. The method of claim 22, wherein said coefficients are difference coefficients, and the iterative computation comprises a series of summations of said difference coefficients to regenerate successive sequential increments of the engraving cuts.
 24. The method of claim 21, further comprising the step of storing the numerical indicia prior to its input into said digital computer.
 25. The method of claim 24, wherein said numerical indicia are stored in a medium consisting of one of the following: a perforated tape, a magnetic tape, a magnetic drum, and punched cards.
 26. The method of claim 21, wherein said numerical indicia comprise coefficients of a plurality of continuous polynomial functions having a commmon parameter, said functions being descriptive of the coordinates defining the cutting paths of the engraving tool in simulating said preselected pattern.
 27. The method of claim 26, wherein said coefficients are difference coefficients.
 28. The method of claim 27, wherein said difference coefficients are summed under the direction of said control program to control the motion of said axis motors. 